This invention relates to the field of fiber optics and, more specifically, to optical switches.
Switches are used in networks to redirect signals along different pathways of a network, thereby enabling networks to adapt to changing conditions. One such changing condition may be to direct signals around a break in an optical fiber. Fiber optic networks typically have more than one path to a particular destination so that, if a fiber breaks, the light signals may be redirect through a second path. Another condition may be to make a temporary point-to-point connection through the network, as might be performed during data transfer.
Regardless of the condition, switching may be performed electrically or optically depending on the particular hardware that is used. However, once signals are converted into optical form, network designers may prefer to maintain the signals in optical form until they reach their destination to reduce system costs and complexity. As such, as transmission rates increase, the need for efficient optical switches continues to grow.
Some optical switches are manufactured using discrete optical elements that may be bulky and expensive. A substantial portion of the cost of making such optical switches arises because the discrete optical elements are physically large and have to be individually and precisely aligned relative to one another. The large size of these components may limit the density with which optical fiber switching systems can be built.
In one type of optical switch, the switching operation is effectuated by moving an input fiber relative to the ends of a group of output fibers that are positioned opposite to the input fiber. To form an optical path, a motor is used to move the end of the input fiber until it is aligned with the end of a selected fiber from the group of output fibers. This type of optical switch is a transmission based device having optical components positioned in series between the input and output fibers. The optical switch includes a lens that is used to focus light from the input fiber to an output fiber.
One problem with a transmission based optical switch is that it requires a large number of optical components to couple light between input and output fibers. The use of a large number of optical components increases the overall length of the optical switch, thereby undesirably adding to its size.
One problem with an optical switch that uses a motor is that it has a slow switching speed and consumes large amounts of power to move the end of the single optical fiber across the entire width of the group of single fibers. Another problem is that the width of optical components must be large enough to couple light between the input fiber and the entire group of output fibers. For example, the lens within the optical switch must be large enough to cover the area in front of the entire group of output fibers. Increasing the length and the width of an optical switch adds to its overall size, thereby decreasing its desirability.
Another type of optical switch includes a Faraday rotator as one of the optical components that are used to selectively couple light between input and output fibers. The Faraday rotator that is used rotates the plane of polarization of light passed through it by 45 degrees. One problem with a 45 degree Faraday rotator is that it is a thick optical element whose use may add to the overall length of the optical switch. The added length may decrease the desirability of such an optical switch.
Yet another type of optical switch uses a single stage to switch light signals between fibers. One problem with single stage switches is that their use may not achieve the degree of isolation required in current optical networks.
The present invention pertains to an optical switch having a plurality of Nxc3x97M optical switchers and a plurality of Mxc3x97N optical switchers coupled to the plurality of Mxc3x97N optical switchers to produce an Nxc3x97N optical switch. M being greater than N and N being greater than 1.
In one embodiment, the optical switchers may have no moving parts and may include a variable magneto-optic rotator that rotates the planes of polarization of light by approximately 22.5 degrees.
Additional features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.